Novel lyophilization cycle development of chitosan based formulation for buccal delivery using paracetamol as a model drug
Ayensu, I., Mitchell , J.C. and Boateng, J.S. (2010) Novel lyophilization cycle development of chitosan based formulation for buccal delivery using paracetamol as a model drug. The AAPS Journal, 12 (S2). ISSN 1550-7416Full text not available from this repository.
Purpose: To develop freeze dried chitosan formulations for buccal mucosa delivery and to determine the effects of plasticization and annealing on their physical properties. Method: 1g of chitosan (medium molecular weight) was dissolved in 50ml of 1% acetic acid and the pH adjusted to 6.5 with 5M NaOH added drop wise. 50ml aqueous solutions comprising mannitol (10%) as cryoprotectant, glycerol (0-50%) as plasticizer and paracetamol (10%) as a model drug were added to give homogeneous gels (1%) and stirred continuously at room temperature (1hour). The resulting gels were freeze-dried in a Virtis Advantage Freeze Dryer. Preliminary thermal characterization by DSC informed the selection of annealing temperature for the novel lyophilization cycle development. The process involved freeze treatment from room temperature to -55°C (2 hours), annealing to -35°C (2 hours) and finally freezing back to -55°C (2 hours). The wafers obtained were evaluated for flexibility, toughness, brittleness, residual water content by gravimetry (heating in an oven and TGA), micro-structure characterisation by SEM and hydration behaviour in aqueous dissolution medium.
Results: Unplasticised wafers were brittle, easily broken along fractured surface (fig. 1a) and instantaneously disintegrated upon contact with dissolution medium whiles high content plasticized wafers collapsed during lyophilization. Optimized concentration of glycerol (10%) however produced flexible, tough and non-brittle wafers (fig. 1b). Annealing facilitated the removal of stresses and softened crystallisable materials thereby improving toughness and reducing brittleness. The mean (+s.d) residual water content of optimized wafers by both gravimetric approaches was 1.9% (+ 0.18) which is consistent with literature optimum range of 1.7 - 4%. The SEM evaluation showed micrographs of plasticized and annealed wafers with porous network which were morphologically stable (fig. 2). This is expected to affect their hydration and swelling behaviour and ultimately drug release characteristics.In addition to plasticizing, glycerol enabled the wafers to swell instead of instantly disintegrating when in they came into contact with dissolution medium.
Conclusion: Stable freeze-dried chitosan wafers have been developed. Plasticization and annealing helped to achieve the desirable physical characteristics of these wafers.
|Additional Information:|| This issue of AAPS Journal, publishes papers from the 2010 FIP Pharmaceutical Sciences World Congress which took place in conjunction with the AAPS Annual Meeting and Exposition on November 14-18, 2010 at the Morial Convention Center New Orleans, Louisiana, USA |
|Uncontrolled Keywords:||freeze-dried wafers, buccal delivery, chitosan|
|Subjects:||Q Science > QD Chemistry|
R Medicine > RM Therapeutics. Pharmacology
R Medicine > RS Pharmacy and materia medica
|School / Department / Research Groups:||School of Science|
School of Science > Department of Pharmaceutical, Chemical & Environmental Sciences
|Last Modified:||31 May 2012 15:26|
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